"There is no doubt" that three big marijuana fields uncovered this month in Ellis and Navarro counties "have a tie to the border and a Mexican drug cartel," said a drug investigator for the Department of Public Safety. "They brought the tenders up here from Mexico to do the work.

"This is not Joe Bob growing some marijuana to smoke. These are professional drug operations," said the investigator, who asked not to be identified for security reasons.

The traffickers’ farming operations, known as "grows," have been an increasing problem on public lands in California and other Western states for some time. But it’s only been in the last two years that the cartels have started to cultivate densely planted plots in North Texas and eastern Oklahoma, law enforcement officials say.

Oklahoma officials got their first glimpse of the trend this summer when an aerial surveillance crew spotted "a buck-naked Mexican in red boots," bathing in a creek in a remote section of the Kiamichi Mountains, said Mark Woodward, spokesman for the Oklahoma Bureau of Narcotics.

Police rappelled into the area from helicopters and found 30,000 marijuana plants spread around multiple plots in the forest, Woodward said. He said the growers used all-terrain vehicles and horses to access the site.

This month alone, sheriff’s departments in Texas’ Ellis and Navarro counties found three irrigated, fertilized and manicured pot-growing operations near Ennis and Corsicana.

More than 16,000 plants have been uprooted from the sites, said Duane Steen, an assistant commander of the Texas Department of Public Safety’s Narcotic Service in Austin.

Last year, a 12,000-plant operation found in Ellis County was the first sign that Mexican drug cartels have branched out from smuggling marijuana to cultivating it in Texas, Steen said.

The Piney Woods of East Texas was where investigators usually found pot patches, Steen said. "The old operations were local: The guy grew up in East Texas and decided to grow a little weed," he said.

What’s being found now is on a different scale.

"It’s not the number of fields, it’s the sheer size of these huge cultivations — 12,000 plants is a lot of marijuana," Steen said.

Ellis County Sheriff Johnny Brown and his drug investigators say they are not surprised at what has become the norm for pot growing.

The marijuana farms were spotted by officers in the department’s surveillance plane, which it got in April through a grant from the National Institute of Justice. "We’re flying every day," Brown said.

"We don’t have our heads in the sand," he said. "It makes good business sense for drug cartels to grow it here. And they are very good businessmen. It’s all about the money.

"If they grow it here, they don’t have to smuggle it across the border and they don’t have to risk driving it 300 miles to get here. There’s little risk for the people behind it and there’s a huge payout."

The potential profits from pot plantations are staggering.

Texas officials said the three plots uncovered this summer would have yielded about 16,000 pounds of high-quality marijuana worth an estimated $24 million, according to a value scale established by the federal Drug Enforcement Administration.

Mike Cox, chief deputy of the Navarro County Sheriff’s Department, said his agency has uprooted a dozen "sophisticated" marijuana plots in the last two years. All told, the plots contained about 40,000 plants, he said.

The largest, a 9,000-plant enterprise found this summer near Angus, three miles south of Corsicana, had water tanks perched on log towers that fed an elaborate drip irrigation system. The elevated tanks were filled from nearby stock ponds through the use of gasoline-powered pumps. The growers even tried to drill a well, Cox said.

The plots have been in heavy woods, and the growers have thinned just enough of the canopy to let filtered sunlight through. "They try to keep the canopy intact so they can’t be spotted from the air," Cox said.

"We tracked the owner, and he’s like Casper the Ghost," he said. "He made a minimum down payment and then made four or five payments, and by the time he was ready to harvest his crop, he quit making payments because he was going to be gone."

Investigators say the plots found in Texas and Oklahoma have something else in common: They were tended by illegal immigrants from Mexico.

"This is the first year that we’ve actually found illegal immigrants, and it was two different very large and high-quality cultivated patches," said Woodward of the Oklahoma narcotics agency. "That may be the new trend, just like what they’ve seen in California. They bring up people from Mexico who know the marijuana-growing business."

In Navarro County, the campsites had a "Hispanic flavor, with Hispanic foods and Hispanic printed material," Cox said.

"Usually what you catch are the poor worker bees that are here illegally. They are paid to water and cultivate. They are living on canned beans and tortillas out in the woods," he said. "The money guys aren’t going to be anywhere near the dope. That’s just business."

Some of the Oklahoma farmers were staying in a cave, and the Texas tenders were living in tents.

"It takes a lot of cultivation and tending. When you have 10,000 plants, you are working all day. It’s hot ... there’s ticks and mosquitoes. It’s rough," he said.

Investigators say identifying good locations for "grows" requires local connections.

It takes people who know the area to find suitable spots that have water sources and that are close enough to roads for transporting manpower, equipment and supplies yet far enough from local activity to provide cover for months at a time.

Ellis and Navarro counties are attractive grow sites for several reasons, investigators say: They are close to the Metroplex, have easy access to interstate highways and offer a mix of rural pockets and medium-size towns like Waxahachie and Corsicana where outsiders can blend in.

The cartels’ increased involvement in marijuana cultivation in the U.S. is a direct offshoot of Mexico’s war on drug traffickers and heightened security on the U.S. side of the border, observers say.

"I think it coincides with when (Felipe) Calderon came in as president and stepped up the war on drug cartels," said Bill Martin, a senior fellow for drug policy at the James A. Baker III Institute at Rice University. "You’ve got walls, fences and more federal presence. They’ve upped the heat on the cartels.

"They’re adaptable, smart and aggressive and have been very successful. Marijuana is a big pie to fight over, and they are willing to do whatever it takes to get their share of it."

The DEA estimates that 60 percent of the cartels’ revenue comes from marijuana.

"We seize more marijuana than anything else on the border," said Rusty Payne, a DEA spokesman in Washington. "A lot of these people would rather do a U.S.-based operation."

The cartels have been most active on public lands in California, and Payne said he was astounded by what he has seen on grows in the Mendocino National Forest in northwestern California.

"There’s always been organized grows, but they are growing in intensity," Payne said.

The problem is cropping up in other states. In August, police found 14,500 pot plants believed to have been cultivated by a drug cartel in the Pike National Forest about 60 miles southwest of Denver.

"This is the first time we’ve discovered these operations in Colorado," said Gill Quintana, special agent in charge of law enforcement in the U.S. Forest Service’s Rocky Mountain Region. "This has been going on for at least 10 years in California. Now they’re spreading throughout the country and going where they feel they can grow the product."

The DPS investigator thinks the publicity about pot on public lands has forced the cartels to seek new fields. "With land you lease, it’s frequently fenced; you can put a gate up and lock it," he said. "There’s still that sense of private-property respect in Texas where you don’t cross the fence. And it’s easy to lease in a fictitious name."

The cartels will keep finding new places to plant crops, says retired California Judge James Gray. "There is so much money in it that they will always be three steps ahead of us. They just change tactics."

Gray, a former federal prosecutor who spent 25 years on the bench in Orange County, Calif., now crusades for the legalization of marijuana.

"It’s getting larger. The more heat you put on in Mexico ... the more they will raise the stuff here," Gray said. "It’s a lost fight. Victory in the war on drugs today is simply slowing the pace of defeat. There will always be people who will supply the stuff, always."

But Payne, the DEA spokesman, says the cartels must be stopped.

"What this marijuana is to drug cartels is their cash cow," he said. "It’s the fuel for the engine. These are huge multimillion-dollar operations, and these drugs are used to buy harder drugs."

The DPS investigator agreed, adding: "It’s huge money for very little investment. It’s great money, and it literally grows on trees."

The recent busts had to have hurt them, he said. But he wouldn’t be surprised to find another giant grow in the region.

"You take $5 million from a big corporation and heads are going to roll," he said. "But if you take $5 million from a drug cartel, they just get back on the phone.

"They are very intelligent people. They are very adaptive: We go left, and they go right. Their livelihood depends on it. But unlike other businessmen, if they lose a lot of money, they’ll kill somebody," he said.

"The part that everyone is missing is that sort of violence occurs here, too. It’s not just in Nuevo Laredo. It’s going on here. I’ve investigated people who got killed for losing a load of dope."